Reaction catalyzed by N,N'-diacetylchitobiose phosphorylase (2.4.1.280)

		+			=			+
	N-acetyl-alpha-D-glucosamine 1-phosphate	+		4-methylumbelliferyl N-acetyl-beta-D-glucosaminide	=		4-methylumbelliferyl N,N'-diacetylchitobioside	+		phosphate